LEOPOLD, ESTELLA B. Botany Department, University of Washington, Seattle WA 98195. - How well do pollen corroborate Eocene leaf taxa?--Florissant Formation,
Colorado, a case study.
The Florissant Fossil Beds National Monument, Colorado, provides a
diverse record of megafossil taxa. Some 110-112 species of vascular
plants described by Harry D. MacGinitie and studied by Steven
Manchester are based on close botanical scrutiny in search of nearest
living relatives. A pollen and spore study of the sediments attempted
to check modern pollen for affinity with all these identifications on
the generic and family level to determine if fossil microspores
matching these leaf identifications can be found. Twenty of the 38
families of vascular plants identified from fossil leaves are
corroborated by pollen and spores. Of the 84 genera, some 26 have been
found in the microfossil record. The 23 genera that microfossil
evidence adds to the flora include several new families not previously
identified at Florissant: among these are Selaginellaceae,
Schizaeaceae, Elaeagnaceae, Rhoipteleaceae, Ericaceae, Onagraceae,
Chenopodiaceae, Eucommiaceae. Further, a member of the
Fremontodendreae has verified the family Sterculiaceae. Three new
conifer taxa of the Pinaceae are added to the flora (Tsuga, an
extinct Cedrus type and Pseudotsuga/Larix). A strong
bias in favor of wind pollinated plant types is apparent: For
example, we can identify affinities with about 3/4 of the
wind-pollinated genera with matching pollen or spores, but only 1/3 of
the genera that are known to be insect-pollinated types producing low
to medium amounts of pollen. The pollen assemblage strengthens the
impression that the flora is of warm temperate to sub-tropical in
aspect, reminiscent of the summer-moist vegetation of Tamulipas, and
Monterrey, in northeastern Mexico.
Key words: Eocene, nearest living relatives, paleoclimate, pollen/spore flora